Transient behavior of viscoelastic fluid in an extruder



A simplified model is used for calculating the time-dependent velocity of polymeric fluid in an extruder. The flow properties of the fluid are characterized by a simple constitutive equation based on two parameters: a constant viscosity μ and a constant elasticity modulus G. It was found that the transient velocity fluctuates periodically, and the time tt needed to restore the steady-state velocity from a disturbance varies with the ratio G/μ and the dimensionless group ρH2G2, where ρ is the density of the fluid and H is the screw depth of the extruder.